In Theogony, Eros is listed as one of the primal gods of the generation after Chaos, the originator. He is the most handsome of the Immortals and can break the will of the wisest god or the strongest mortal when they are scratched by one of his arrows.
With arrows of gold and lead, he can wound the hearts of mortals and Olympians alike. The golden arrows inspire love and the lead arrows cause distaste. In Theogony (line 120), it's said emphatically that 'Eros is love.' The negative aspect, with the lead arrows, was added at a later date.
The Trojan War began when Helen, the daughter of Zeus, was smitten by Eros's arrow. In the blind madness of love, she abandoned her husband, took her bridal dowry and sailed off to Troy with her lover, Alexandros (Paris). We can assume that Eros's enchantment can wear off because after the sack of Troy we find Helen at home with her rightful husband Menelaos (Menelaus), very much in love. She blamed her folly on Zeus who had commanded Eros to smite her with love.
There is an interesting story related in The Argonautika where Eros had an encounter with the cup-bearer of the Immortals, Ganymede (Ganymedes). A generation before the Trojan War, Jason and the Argonauts were sent to the land of Kolchis (Colchis) at the eastern edge of the (the Black Sea) to retrieve the Golden Fleece from King Aietes (Aeetes). Jason was under the protection of the goddess Hera who protected him and gave him her divine assistance. Hera knew that King Aietes would not voluntarily surrender the prized Golden Fleece so she decided to use the king's daughter, Medeia (Medea), to help Jason steal the Fleece. Hera asked Aphrodite to persuade Eros to strike Medeia with an arrow of irresistible love for Jason so that she would be immune to her father's control and assist Jason in his quest to obtain the Golden Fleece and return it to his home at Iolkos (Iolcos).
Ganymede was one of the three sons Tros who was, in turn, the great-grandson of Zeus and the great-grandfather of Priam, who was the last king of Troy. He was abducted by Zeus and taken to Mount Olympos (Olympus) where he was made the cup-bearer of the Immortals and thus became immortal himself. When Aphrodite went to Mount Olympos to see Eros, the young god was playing dice with Ganymede. Aphrodite scolded Eros for cheating an innocent child. She then asked Eros to strike Medeia with one of his arrows of Love. She promised him a golden ball that, when thrown into the air, would flair like a meteor if he would do her bidding.
Eros did as Aphrodite wished and Medeia was irresistibly attracted to Jason. Medeia evoked the goddess Hekate (Hecate) to protect Jason and used her knowledge of spells and enchantments to assist Jason. She used her supernatural powers to subdue the dragon that guarded the Golden Fleece and, once they had made their escape from Kolchis, assisted Jason in the cold blooded murder of her stepbrother, Apsyrtos. The power that Eros wields over mortals is unimaginable.
We often think of Eros as an infant but he is usually depicted in ancient artwork as a young man. Eros is one of the oldest of the Immortals and was the forth Immortal to come into existence. Eros was preceded by Chaos (the first Immortal), Gaia (Earth) and Tartaros (the Pit). His age cannot be estimated but he existed eons before the Olympian Immortals came to power.
Eros playing dice
Eros was a very popular theme for ancient artists. His likeness can be found on ceremonial as well as household items. I have collected these images from various museums and you may see them with the fillowing link ... Images of Eros.
(The fragment number listed here is from the Loeb Classical Library vol. 503, Hesiod II)